The current invention relates to an improved heat exchanger fin, and more particularly, an improved heat exchanger fin that can be used to control an undesirable temperature gradient caused by the natural conductive tendencies of the fins of a heat exchanger. Minimizing undesirable temperature gradient along an undesirable direction within the heat exchanger fins increases a convective heat transfer along the desired direction, thus increasing the performance of the heat exchanger.
As electromechanical components inevitably get more and more complicated, there is an increased need to minimize the size of heat exchangers of such electromechanical components while at the same time increasing the heat exchange rate. Because so much of the efficiency of the heat exchanger is dependent upon the heat exchanger fins themselves, it is desirable to try and maximize the efficiency heat exchanger fins within a heat exchanger.
Newton's law of cooling sets up the basis of thermal heat energy transfer Q as a function of the heat transfer coefficient h, surface area for heat transfer A, and the temperature difference of the two surfaces (To−Tenv). The formula below sets up the relationship of the above mentioned variable.
                                          ⅆ            Q                                ⅆ            t                          =                  h          *                      A            ⁡                          (                                                T                  O                                -                                  T                  env                                            )                                                          (        1        )            
Based on the above equation (1), it can be seen that one of the ways to increase the thermal heat energy transfer Q is to increase the heat transfer coefficient h. In order to increase the heat transfer coefficient h, materials having high conductivity such as silicon and copper can be used to make the fins of the heat exchanger which results in an increased thermal heat transfer rate Q. However, increase in conductivity of a heat exchanger fin material can only be limited to conductivity of the materials themselves, thus limiting the developments in this respect.
Alternatively, another way to increase heat transfer Q is to increase contact surface area A. By increasing the contact area A between a hot fluid and a cold fluid, there is more surface area A to transfer heat between the two fluids. However, increasing the contact surface area A of the heat exchanger also tends to increase the overall size of the heat exchanger itself, making it undesirable in situations where an increase in size is undesirable.
In order to address the need to increase contact surface areas A while minimizing the size of the heat exchangers, improvements in creating fin geometries that dramatically increase the contact surface area A without any major sacrifice to the overall size of the heat exchanger have led to the developments of microchannel heat exchanger fins. In accordance with the microchannel concept, circular and rectangular microchannel heat exchangers have also been employed in compact heat exchangers due to superior performance based on their geometric composition.
Although microchannel heat exchangers have been the answer to maximizing contact surface area A, they may conduct heat within the microchannel heat exchanger fins themselves. The conduction of heat within the microchannel heat exchanger fin creates an undesirable temperature gradient within the microchannel heat exchanger fin itself. This conductive effect called “matrix conduction” generally occurs when the heat exchanger is faced with extreme levels of heat and the proximity of the microchannels within the microchannel heat exchanger fin allows conduction of thermal energy. Matrix conduction generally results in heat conduction occurring in an undesired direction, causing the convective heat transfer performance along the desired direction to suffer. Ultimately, matrix conduction within a fin of a microchannel heat exchanger is undesirable, as it decreases the performance of heat transfer from the hot fluid to the cold fluid along the desired direction of flow.
Hence, it can be seen that there is a need for an innovative microchannel heat exchanger that increases the heat transfer coefficient h, while at the same time addressing the adverse matrix conduction problem occurring within the individual fins themselves, all while maintaining the lightweight, compact design of a heat exchanger without sacrificing convective heat transfer.